Electric blasting cap



July 19, 1938. w. c, HUNT 2,123,996

July 19, 1938.

W. C. HUNT ELECTRIC BLASTING CAP Filed April 10, 1936 2 Sheets-Sheet 2FIG.5

FIG.4

FIG.7

FIG.6

S M N M 2 R E W V T A Y B M M Patented July 19, 1938 UNITED STATESPATENT OFFICE Application April 10, 1936, Serial No. 73,602

4 Claims.

.This invention relates to a new and improved electric blasting cap,such as is used in firing commercial explosives, and more particularlyrelates to an arrangement whereby blasting caps may be protected duringshipment and storage,

with avoidance of accidental discharge.

As is well known, electric blasting caps are equipped with a pair oflead wires, by which they are connected to a firing circuit after theyhave been placed within an explosive charge to be detonated. Usually,forthe purpose of shipment and storage of such electric blasting caps,the lead wires, often of considerable length, are bundled and tiedcentrally of thewire bundle, with the free ends of the lead wires andthe v cap at opposite ends of the bundle.

The customary bundling and tying of the lead wires .of such caps isordinarily sufficient to enable packaging and handling of the caps, but,since the cap itself is wholly unprotected, it is liable to accidentalfiring by any shock to which it may be subjected, for example, bystriking another cap in the package, or by striking the wall of apackage during shipment, from being 25 dropped during handling, orotherwise. Such caps are usually loaded with mercury fulminate,

diazodinltrophenol, or similar, sensitive high explosive, so that thepossibility of accidental firing presents a certain amount of hazard.

Heretofore, attempts have been made to avoid this disadvantage of havingthe cap exposed to shock, e. g. as in United States Let ers Patents1,912,432 and 1,631,756, but such attempts have not wholly accomplishedtheir purpose, or have 35 involved serious difficulties in removing thelead wires from the bundle without tangllng the wires. Moreover, suchattempts in the past have necessitated the use of separate elements toform the core and the protective sleeve and' the insertion 40 of thewire bundle within said sleeve element, all at considerable cost ofmaterials and labor in packing such electric blasting caps.

It is theobject of this invention to provide an arrangement consistingof the lead wires only, whereby such caps will be adequately protectedfrom shock, whether during shipment, storage, or handling, and at thesame time provide a ready method of dis-assembling the package without50 tangling the lead wires.

In accordance with this invention there is provided a protector for theblasting cap in the form' of a self-supporting coil, without the use ofa sleeve or tube to form either core of the coil or tsprotecticn overthe coil, such as has been necessary in the past withhelically woundlead wires.

Having now indicated in a general Way the nature and purpose of myinvention, I shall proceed to a detailed description of preferredembodiments thereof, with reference to the accompanying drawings, inwhich Figure 1 is a side view of an electric blasting cap packageembodying my invention, Figure 2 is a view in elevation of the device ofFigure 1, Figure 3 is a modification. of the device of Figure 1, Figure4 an end view of the device embodying my invention where it is desiredto use the invention on short lengths of lead wires, and Figure 5 a sideview of the device of Figure 4, Figure 6 an end view of a modificationof the device of Figures 4 and 5, and Figure '7 a side view of thedevice shown in Figure 5.

Referring more particularly to Figure l of the accompanying drawings, lindicates an electric blasting cap, provided with lead wires 2 which arewound, beginning with the lead wires adjacent to the cap, in the form ofwhat is commonly known as a honeycomb coil," by moving the lead wires,uring the coiling operation on a mandrel whose diameter is approximatelythe length of the blasting cap, from one end of the coil to the other,so that said lead wires cross the wires beneath them at an angle to theunderlying wires, and also form a lock for the underlying wires at theends of the coil, to prevent collapse of the coil, allas is shown ingreater detail in Figures 2, 5, and 7. When the coil has been wound asdescribed, a loop, 2 is formed from the the extending ends of the leadwires, and the end of lead wires 2 passed through said loop, the loopplaced about the exterior of the honeycomb coil, pulled tight, and theends of the lead wires 2 bent back to lock the loop in place. The coilis then removed from the mandrel, and will be found to be interlockedfrom layer to layer and will be self-supporting, being prevented fromuncoiling by the exterior loop '2 The blasting cap I is then insertedinto the open space forming the core of the coil and is retained thereby resting with the base of the blasting cap pressed against theinterior of the coil by the spring effect of lead wires 2. Theuninsulated ends of thelead wires 2 may be suitably short-circuited, bytwisting them together or by twisting them, as shown by 2', about a barepiece of heavier wire 3.

.It will be noted that to uncoil the lead wires for use in blastingoperations, it will be necessary only to pull the blasting cap I fromthe core of the coil, whereupon lead wires 2 uncoil from the interior ofthe honeycomb coil as the lead wires arepulled forth, and do so withoutinterference from any pasteboard coil core heretofore used, and withoutcurling or kinking, as has been experienced with blasting cap coilsheretofore employed.

Referring now specifically to Figure 3 of the accompanying drawings,which represents a modification of my invention shown in Figure 1, itwill be noted that thehoneycomb coil of the lead wires is formed bywinding on a mandrel whose diameter is approximately the length of theblasting cap, the lead wires 2 starting from the uninsulated extremitiesof said lead wires 2', forming a loop 2 of the lead wires 2 after thecoil is wound, putting the blasting cap l and lead wires "through saidloop and bending back cap and lead wires to form a lock, then placingthe blasting cap within the core of the honeycomb coil with the bottomof the blasting cap resting against the interior of the core of the coiland retained in position by the spring of lead wires 2.

It will be noted that, in the form of my invention shown in Figure 3,the bare ends (2') of the lead wires are protected from contact withsources of electricity by being within the core of the honeycomb coil,--and consequently do not ordinarily require short-circuiting forprotection from stray currents, while at the same time the blasting capis also protected from striking objects by being within the hollow coreof the coil. It will also be noted that this form of my invention alsoenables the lead wires to be uncoiled from the center of the honeycombcoil by merely pulling out the end 2 of the lead wires, and this withoutthe undesirable curling and kinking heretofore experienced with otherforms of cap packages.

Referring now specifically to Figures 4 and 5 of the accompanyingdrawings, which illustrate a preferred embodiment of my invention withthe use of comparatively short lengths of lead wire, i represents theblasting cap, 2 the lead wires of said blasting cap, 2 the uninsulatedends of said lead wires, and 4 a band or strap, e. g., of tape or rubberband, to tie down the last convolution of the honeycomb coil. In thisembodiment of my invention, the lead wires 2 are coiled in thecriss-cross, honeycomb manner hereinbefore described, upon a mandrelwhose diameter is slight- 1y greater than the diameter of the blastingcap, commencing with the portions of the lead wires nearest the cap,and, when the coil has been formed, the coil is removed from themandrel, the blasting cap inserted in the core of the coil, where it isretained by the spring effect of lead wires 2, and by the retaining bandor strap d placed about the exterior of the coil.

Referring now specifically to Figures 6 and 7 of the accompanyingdrawings, which represent a modification of my invention shown inFigures 4 and 5, it will be noted that the winding of the honeycomb coilis commenced with the uninsulated' ends of the lead wires, and, afterthe winding of the coil is completed, the cap and its lead wires arethen inserted into the hollow case of the coil and retained there by thespring effect of the lead wires. The band or strap 5 is used on theexterior of the coil, as hereinbefore described.

It will be noted that in the form of my invention shown in Figures 4 to7 inclusive, the uncoiling of the lead wires before use in blastingoperations will be from the interior of the honeycomb coil, without theusual disadvantages of curling and kinking heretofore experienced.

In the winding of the lead wires to form the honeycomb coil of myinvention I prefer to use coil winders ordinarily used to form suchcoils, although I may use any suitable apparatus therefor.

It will be noted particularly, that I do not require any supports or endpieces for my honeycomb coil, nor, as has been stated, any tube with .inthe coil. Thus, except for the binding strip of Figures 5 and 7, I formmy blasting cap package solely of the lead wires per se, without resortto the use of any additional materials.

It will be noted that my blasting cap assembly lends itself withadvantage to the packing of several such coils in one box, without thecomplication of entangling lead wires of one blasting cap with another,and without the large packing box or case heretofore required.

What I claim and desire to protect by Letters Patent is:

1. A prepared package comprising a blasting cap having a pair of leadwires wound in the form of a substantially rigid self-supporting,honeycomb coil, the blasting cap being within said honeycomb coil.

2. A prepared package comprising a blasting cap having a pair of leadwires wound in the form. of a substantially rigid self-supporting,honeycomb coil, the blasting cap being within said honeycomb coil, and a'wire tie composed of the end portion of the lead wires about theexterior of said coil and adapted to prevent uncoiling of said coil.

3. A prepared package comprising a blasting cap having a pair of leadwires wound in the form of a substantially rigid self-supporting,honeycomb coil, said coil having a core diameter approximately thelength of said blasting cap, and a blasting cap in said core of saidhoneycomb coil.

4. A prepared package comprising a blastng cap having a pair of leadwires wound in the form of a substantially rigid self-supporting,honeycomb coil, said coil having a core diameter approximately thediameter of said blasting cap, and a blasting cap in said core of saidhoneycomb coil.

WILLIAM C. HUNT.

